1. Field of the Invention
The present invention relates to catalysts comprising chiral monophosphorus compounds and their use, the chiral monophosphorus compounds themselves and also their precursors. For the purposes of the invention, chiral monophosphorus compounds are, in particular, chiral monophosphites, monophosphoramidites and monophosphonites.
2. Brief Description of the Prior Art
It is already known that chiral monophosphites or their transition metal complexes can be used for asymmetric syntheses (cf. A. Alexakis, Tetrahedron Asymmetry, 1997, 8, 3193–3196; C. Claver et al., Chem. Commun., 2000, 2383–2384; W. Chen, J. Xiao, Tetrahedron Letters, 42, 2001, 2897–2899; M. Reetz, G. Mehler, Angew. Chem., 2000, 112, 4047–4049). The use of chiral monophosphoramidites or their transition metal complexes in asymmetric syntheses is known, for example from van den Berg et al., J. Am. Chem. Soc., 2000, 122, 11539–11540, and H. Waldmann, Chem. Eur. J. 2000, 6, 671–675, and the use of chiral monophosphonites is known from C. Claver et al., Chem. Commun., 2000, 961–962.
However, all chiral ligands known hitherto are derived from the basic framework of 2,2′-dihydroxy-1,1′-binaphthyl or other polycyclic dihydroxybisaryls. The disadvantage of such ligands is that only limited substitution opportunities are available for varying the electronic and steric properties. Use in various asymmetric reaction types and applicability to many substrates does, however, make a broad range of possible substitutions desirable.
Furthermore, there is a need to develop catalysts which, particularly when used in asymmetric hydrogenations, give not only a high enantioselectivity but also high conversions and mild to moderate reaction conditions.